Integrated optoelectronic chips or collections of chips on a module that have both electrical as well as optical interconnects offer many advantages in speed, power consumption and heat generation. Mixed signal types, however, pose significant packaging challenges. This invention describes a land grid array (LGA) interposer which can simultaneously connect electrical and optical signals from a module to a printed circuit board.
In a mixed optical electrical LGA interposer (OELGA) there are a plurality of electrical contacts which are constructed to have conducting elements extend in both directions perpendicular to the plane of the interposer with the purpose of connecting a BLM from a module above to the TLM of a PWB below. These conducting elements or contacts (aka buttons) can be composed of a variety of materials and geometries but always have both conducting and mechanical compliance (spring) functions. There are also one or more optical interconnects (windows) which have the dual functions of optical transparency and mechanical compliance. These compliant optical windows can be conveniently fabricated from silicone rubber injection molded directly into place in the desired form.
The proper combination of electrically conductive buttons and optical windows allow a chip module that has both electrical and optical chips to communicate through the LGA onto the circuit board.
An alternative to such spring-loaded windows might be simple openings in the LGA which would allow the optical signals to pass. However, the omission of a compliant window would allow introduction of dust which could block the optical path and lead to reliability concerns. Thus, the preferred embodiment of this patent utilizes such a compliant window to create a dust free, uninterrupted optical path.
There are a great variety of conceivable arrangements that would apply to different ratios of electrical to optical signals, to different laser and detector choices, different pitch, pin count, and so forth as would be obvious to those skilled in related arts.